According to US air safety officials, the glitch that caused travel chaos at airports last week was caused by a contractor deleting files on a critical computer server used by pilots.
The Federal Aviation Administration (FAA) stated that the worker “unintentionally deleted files” from the Notam database.
The system warns pilots of potential hazards along flight paths. They are required to inspect it prior to flights.
Lawmakers promised to look into the matter.
After the Notam system went down a day earlier, more than 11,000 flights were delayed and at least 1,300 were cancelled on January 11.
Flights across the United States were grounded for the first time since the September 11, 2001, terrorist attacks.
The FAA stated that an unidentified contract employee deleted the files while working to synchronize the primary and backup Notam databases.
Why did the FAA ground flights across the United States?
Two planes almost collide on a runway at a US airport.
“The agency has found no evidence of a cyber-attack or malicious intent thus far,” the regulator said in a statement released on Thursday.
The FAA went on to say that they were still looking into the error. The system was repaired, and the FAA “has taken steps to make the Notam system more resilient,” according to the statement.
The outage had previously been blamed on a “damaged database file,” according to the FAA.
Last week, a group of Washington, DC lawmakers wrote to the FAA, saying the outage was “completely unacceptable” and asking how it could be avoided in the future.
On Friday, FAA acting Administrator Billy Nolen plans to hold a virtual briefing for lawmakers to address their concerns.